Animation Nodes's vector distance : can't make it work like in the official example
The Empty in your blend file isn't in the boxes' plane but 8.4 BU above it. With the current node setup the boxes will only be affected when the Empty is closer to 1 BU to the boxes' center, which perhaps didn't happen if you only moved the Empty in top view.



If the Empty is moved within the Z=0 plane the boxes will scale correctly.

You might also want to consider adding a Math/Multiply node after the Vector Distance node, or use smaller boxes, if you want to affect more than one box at a time. With the current size of your boxes only one of them will be closer than 1 BU to the Empty.